Cnidocytenematocyst

Cnidocytenematocyst is a term used to describe the stinging organelle system within cnidocytes of cnidarians. A cnidocyte is a specialized cell that houses a nematocyst, a capsule loaded with a venomous tubule. Together, the cnidocyte and its nematocyst form the functional unit used for prey capture and defense. The term itself is a descriptive way to refer to the nematocyst contained inside the cnidocyte.

The nematocyst consists of a capsule wall and a long, coiled tubule that stores venom. When a cnidocil, a hairlike trigger on the cnidocyte, is stimulated chemically or mechanically, a rapid influx of ions causes the capsule to open and the tubule to evert in a fraction of a second. The discharged tubule can puncture the target, entangle it, or adhere to surfaces, delivering venom through tiny pores along its length. Discharge is extremely fast and can be accompanied by accompanying structures such as spines or barbs depending on the nematocyst type.

Nematocysts show diversity in form and function. Functional types include penetrants that puncture, glutinants that attach, and volvents that deploy a wrapping thread. Toxins vary among species and can affect prey or potential predators; in humans, stings range from mild irritation to severe pain and, rarely, systemic effects. Cnidocysts are renewed as cnidocytes turn over, and their distribution across cnidarians underpins many feeding and defensive strategies in this phylum.